The objective of the proposed research is a greater understanding of the regulation of Ig biosynthesis and of the structural requirements for Ig function. We will use recombinant DNA technology and gene transfection to determine the structural basis of human IgG effector function and to create IgG molecules with novel combinations of effector functions. We will put linkers on the different domains of the IgG molecules and create novel domain combinations and molecules with domain deletions. Using in vitro site directed mutagenesis, we will destroy the carbohydrate addition site in CH2. The novel constant regions will be ligated to variable regions from antigen binding myelomas and transfected into mouse myeloma cells along with a light chain with a V region from the same antigen binding myeloma attached to either human C-Kappa or C-Lambda. Stable transfectants will be selected and characterized with respect to their ability to synthesize, assemble, and secrete the chimeric Ig molecules. Using either culture supernatants or ascites fluid from tumor bearing mice, the functional properties of the chimeric Ig molecules will be characterized. Among other things we will determine their ability to bind antigen, to fix complement, to bind to cellular receptors, and their intervascular stability. In a second series of experiments, we will characterize regulatory regions within immunoglobulin genes and attempt to identify and isolate the factor(s) which lead(s) to their utilization. Using a CAT expression assay we will determine if there is evidence for a limiting quantity of a "factor" which is necessary for the expression of Kappa light chain genes and if H and L chain regulatory regions and the different regulatory regions within the L chain compete for the same factors. In addition we will determine if cells at different differentiation states (i.e., B and T lymphocytes, plasma cells, non-lymphoid cells) produce factors with the same apparent binding specificity. Using both the competitive CAT assay and the fact that the presence of enhancer regions lead to increased gene transfection frequencies, we will search for enhancer regions within mouse and human Lambda genes. In addition, we will attempt to establish an in vitro assay for factor binding. If an accurate, reliable assay can be established, we will attempt the isolation of the light chain enhancer binding factor.